Corn Yield Trends for Indiana 1930 - 2000

Historical grain yields provide us with a glimpse of yields yet to come,
although like the stock markets, past performance is no guarantee of the
future. State average corn grain yield in Indiana has increased at a fairly
constant 1.6 bushels per acre per year since 1930 primarily due to improved
genetics and production technology (Fig. 1).

Indiana's corn crop yield has split even during the past ten years, with
half of those years below trend and half above. The
November USDA estimate for 2000 puts the 2000 Indiana corn
crop at 147 bushels per acre, or 7.8 percent above the 2000 trend line yield.
By comparison, other recent dramatic positive departures from trend yield were
1982 (16.9 %), 1987 (16.6 %), 1992 (18.8 %) and 1994 (13.5 %). Corn production
estimates for each crop reporting district in Indiana can be found in
tabular or
graphical formats.

Fig. 1

While some point to the consistent 1.6 bu/ac/yr yield gain as a
comforting signal that growers and researchers are continuing to be successful
in their search for ever-increasing yields to feed the hungry world, others
point out that the relative annual yield gain has been decreasing for years.
Indeed, because the absolute annual yield gain has been relatively consistent,
the relative annual yield gain for corn has been steadily decreasing (Fig. 2).

Fig. 2

Annual grain yield values fluctuate above and below the trend line
throughout the nearly 70 year period of records, but four disaster years are
especially noteworthy. Late planting plus early fall frosts in 1974 resulted in
state average corn yields 25% less than the trend value. Severe droughts in
1983, 1988 and 1991 resulted in yields 33%, 29% and 25% less than trend values.

Because the departures from trend for these four years are so dramatic,
it is of some interest to calculate the trend line for corn grain yield without
their inclusion. In so doing, the annual rate of yield increase is slightly
greater (1.7 versus 1.6 bu/ac/yr) and the estimated trend yield for 2000
changes from 136.4 to nearly 142 bushels per acre (Fig. 3). Such values may be
more true estimates of statewide yield potential in "normal" years.

Fig. 3

The top five U.S. corn grain producing states are Iowa, Illinois,
Nebraska, Minnesota and Indiana (Fig. 4). As of November 1999, these five
states (6.194 million bushels) accounted for over 64 % of the total estimated
grain yield for the U.S. in 1999 (9.537 million bushels).

Fig. 4

Interestingly, the trophy for top statewide yields per acre does not
belong to any of these Midwestern states. Bragging rights for highest U.S. corn
yields per acre belong to states farther to the west (Fig. 5). A few reasons
for this include a) fewer cloudy and hazy days, b) less rainfall and humidity
contributing to less disease, c) availability of irrigation, and d) fewer
stressful hot nights during grainfill.

For other
information about corn, take a look at the Corn Growers Guidebook on the World
Wide Web at http://www.kingcorn.org

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Agronomy Department that all persons shall have equal opportunity and
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employer. This material may be available in alternative formats.